The invention relates to a circuit and method for masking bits.
In some digital operations involving the comparison of two operands, it is desirable to exclude or "mask" some bits of the operands from the operation so that their unmasked binary values have no effect on the output of the operation. To accomplish this, TRIT (TeRniary digIT) logic, also referred to as 3-value logic, is often used. TRIT logic can store one of three states, namely, ZERO (0), ONE (1), and DON'T CARE (X). Thus, for example, when a bit of a dataword is compared to the stored state, the TRIT logic outputs a ONE, indicating a match, if the stored state is identical to the dataword bit or if the stored state is a DON'T CARE state. Otherwise, the TRIT logic outputs a ZERO, indicating no match. Using TRIT logic, however, generally doubles the word width for a given data transfer rate or halves the data transfer rate for a given word width. This is because two bits are required per TRIT logic to express the three different states.